Dyes known to oxidation dyes, which are produced by oxidative coupling of a developer component with a coupling component, are preferred due to their intense colors, the mild reaction conditions under which they are formed, and their very good fastness properties. Nitrogen bases such as primary aromatic amines with an additional hydroxyl or unsubstituted or substituted amino group in ortho or para position, diaminopyridine derivatives, 4-amino-pyrazolone derivatives, heterocyclic hydrazone derivatives, and tetraaminopyrimidines are generally used as developer substances. Phenols, m-phenylenediamine derivatives, naphthols, certain resorcinol derivatives, and pyrazolones are known to be useful as coupling components.
Good oxidation dyestuff components must meet the following requirements:
They must produce the desired color nuances in sufficient intensity during oxidative coupling with the respective developer or coupling component. Also, they must possess a capacity for being absorbed by human hair without excessive coloring of the scalp. In addition, they should be toxicologically and dermatologically safe.
The production of the strongest possible color shades closely corresponding to the natural hair color nuances is also important. Furthermore, the general stability of the dyestuffs produced as well as their fastness to light and to washing and their thermostability, have very special significance for the prevention of color shifts from the original color nuance or even a change in color to different shades. In addition, in the hair dyeing field there is always an interest in new oxidation dye components that can be combined with the known dye components to produce new color nuances of cosmetic value.
The use of resorcinol as a coupling component is known from German patent specification Nos. 162,625 and 276,761. Other resorcinol derivatives, for example, alkyl- and di-alkyl-m-dihydroxybenzenes, were suggested as coupling components for oxidation hair dyes in U.S. Pat. No. 4,003,699. However, the resistance characteristics of the hair colors obtainable with resorcinol and the known resorcinol derivatives are not satisfactory. For example, resorcinol and 2-methylresorcinol in combination with many conventional developer components, for example, with tetraaminopyrimidines, produce colors that have a tendency to turn red when they are exposed to light and heat.
Thus, the search for suitable oxidation hair dyes includes the task of finding the proper components that meet the above-mentioned prerequisites in an optimal fashion.